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Title: Proton radius from electron scattering data

Journal Article · · Physical Review C
 [1];  [2];  [3];  [1];  [4];  [1]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  2. Kent State Univ., Kent, OH (United States). Dept. of Physics
  3. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Western Branch High School, Chesapeake, VA (United States)
  4. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Physics

Background: The proton charge radius extracted from recent muonic hydrogen Lamb shift measurements is significantly smaller than that extracted from atomic hydrogen and electron scattering measurements. The discrepancy has become known as the proton radius puzzle. Purpose: In an attempt to understand the discrepancy, we review high-precision electron scattering results from Mainz, Jefferson Lab, Saskatoon and Stanford. Methods: We make use of stepwise regression techniques using the F-test as well as the Akaike information criterion to systematically determine the predictive variables to use for a given set and range of electron scattering data as well as to provide multivariate error estimates. Results: Starting with the precision, low four-momentum transfer (Q2) data from Mainz (1980) and Saskatoon (1974), we find that a stepwise regression of the Maclaurin series using the F-test as well as the Akaike information criterion justify using a linear extrapolation which yields a value for the proton radius that is consistent with the result obtained from muonic hydrogen measurements. Applying the same Maclaurin series and statistical criteria to the 2014 Rosenbluth results on GE from Mainz, we again find that the stepwise regression tends to favor a radius consistent with the muonic hydrogen radius but produces results that are extremely sensitive to the range of data included in the fit. Making use of the high-Q2 data on GE to select functions which extrapolate to high Q2, we find that a Pad´e (N = M = 1) statistical model works remarkably well, as does a dipole function with a 0.84 fm radius, GE(Q2) = (1 + Q2/0.66 GeV2)-2. Conclusions: Rigorous applications of stepwise regression techniques and multivariate error estimates result in the extraction of a proton charge radius that is consistent with the muonic hydrogen result of 0.84 fm; either from linear extrapolation of the extreme low-Q2 data or by use of the Pad´e approximant for extrapolation using a larger range of data. Thus, based on a purely statistical analysis of electron scattering data, we conclude that the electron scattering result and the muonic hydrogen result are consistent. Lastly, it is the atomic hydrogen results that are the outliers.

Research Organization:
Univ. of Virginia, Charlottesville, VA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
SC0014325; AC05-060R23177
OSTI ID:
1417866
Alternate ID(s):
OSTI ID: 1254887
Journal Information:
Physical Review C, Vol. 93, Issue 5; ISSN 2469-9985
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 47 works
Citation information provided by
Web of Science

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Cited By (12)

Efficient Bayesian shape-restricted function estimation with constrained Gaussian process priors journal January 2020
A small proton charge radius from an electron–proton scattering experiment journal November 2019
Deuteron charge radius and Rydberg constant from spectroscopy data in atomic deuterium journal March 2017
Virtual Delbrück scattering and the Lamb shift in light hydrogenlike atoms journal September 2019
Proton Charge Radius from Electron Scattering journal December 2017
Computing the nucleon charge and axial radii directly at $Q^2=0$ in lattice QCD text January 2018
Measurement of two-photon exchange effect by comparing elastic e±p cross sections text January 2017
Codata Recommended Values Of The Fundamental Physical Constants: 2014 text January 2015
Proton radius from electron-proton scattering and chiral perturbation theory text January 2016
Nucleon form factors in dispersively improved Chiral Effective Field Theory II: Electromagnetic form factors text January 2017
Revisiting the proton-radius problem using constrained Gaussian processes text January 2018
Proton charge radius extraction from electron scattering data using dispersively improved chiral effective field theory text January 2018

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